Method of preparing crystalline zeolite

ABSTRACT

A method of preparing zeolite ZSM-5 type crystals and mixtures thereof which comprises crystallizing the substantially pure zeolite material from a silica and, optionally, alumina gel mixture in the presence of an alkylammonium-N-oxide cation, and the products produced thereby.

FIELD OF THE INVENTION

This invention relates to an improved method of preparing crystallinezeolite materials using a new class of compounds 1-alkyl, 4-aza,1-azonia-bicyclo(2,2,2)octane, 4-oxide, halides.

DESCRIPTION OF THE PRIOR ART

Zeolitic materials, both natural and synthetic, have been demonstratedin the past to have catalytic properties for various types ofhydrocarbon conversions. Certain zeolitic materials are ordered, porouscrystalline aluminosilicates having a definite crystalline structurewithin which there are a large number of channels. These cavities andchannels are precisely uniform in size. Since the dimensions of thesepores are such as to accept for adsorption molecules of certaindimensions while rejecting those of larger dimensions, these materialshave come to be known as "molecular sieves" and are utilized in avariety of ways to take advantage of these properties.

Such molecular sieves, both natural and synthetic, include a widevariety of positive ion-containing crystalline aluminosilicates. Thesealuminosilicates can be described as a rigid three-dimensional frameworkof SiO₄ and AlO₄ in which the tetrahedra are cross-linked by the sharingof oxygen atoms whereby the ratio of the total aluminum and siliconatoms to oxygen is 1:2. The electrovalence of the tetrahedra containingaluminum is balanced by the inclusion in the crystal of a cation, forexample, an alkali metal or an alkaline earth metal cation. This can beexpressed wherein the ratio of aluminum to the number of variouscations, such as Ca/2, Sr/2, Na, K or Li is equal to unity. One type ofcation may often be exchanged either entirely or partially by anothertype of cation utilizing ion exchange techniques in a conventionalmanner. By means of such cation exchange, it has been possible to varythe properties of a given aluminosilicate by suitable selection of thecation. The spaces between the tetrahedra are usually occupied bymolecules of water prior to dehydration.

Prior art techniques have resulted in the formation of a great varietyof synthetic aluminosilicates. These aluminosilicates have come to bedesignated by letter or other convenient symbols, as illustrated byzeolite A (U.S. Pat. No. 2,882,243), zeolite X (U.S. Pat. No.2,882,244), zeolite Y (U.S. Pat. No. 3,130,007), zeolite ZK-5 (U.S. Pat.No. 3,247,195), zeolite ZK-4 (U.S. Pat. No. 3,314,752) zeolite ZSM-5(U.S. Pat. No. 3,702,886), zeolite ZSM-11 (U.S. Pat. No. 3,709,979),zeolite ZSM-12 (U.S. Pat. No. 3,832,449), zeolite ZSM-20 (U.S. Pat. No.3,972,983), zeolite ZSM-35 (U.S. Pat. No. 4,016,245), zeolite ZSM-21 and38 (U.S. Pat. No. 4,046,859), and zeolite ZSM-23 (U.S. Pat. No.4,076,842), merely to name a few.

SUMMARY OF THE INVENTION

The novel class of compounds discovered to be useful in the presentzeolite synthesis are described in co-pending U.S. Application Ser. No.073,766 filed Sept. 10, 1979 filed concurrently herewith.

The present invention relates to an improved method of preparingsynthetic crystalline zeolite materials having a constraint indexbetween 1 and 12 and a SiO₂ /Al₂ O₃ ratio greater than 5. Moreparticularly the present invention relates to an improved method ofpreparing the zeolites ZSM-5, ZSM-11, ZSM-12, ZSM-21, ZSM-23, ZSM-35,ZSM-38 and ZSM-48 described in our copending U.S. Application Ser. No.13,640 filed Feb. 21, 1979.

Still more particularly, the present invention is directed to animproved method for preparing a group of crystalline zeolite materialshereinafter designated as ZSM-5 and an unidentified crystalline materialwhich comprises crystallizing the substantially pure zeolite materialfrom a silica and alumina (optional) gel mixture in the presence of anew class of compounds 1-alkyl, 4-aza, 1-azonia-bicyclo (2,2,2)octane,4-oxide, halides and the zeolite products produced thereby.

DESCRIPTION OF PREFERRED EMBODIMENTS

Zeolite ZSM-5, for example, has the formula, in terms of mole ratios ofoxides as follows:

    0.9±0.2 M.sub.2/n O:Al.sub.2 O.sub.3 :Y SiO.sub.2 :zH.sub.2 O

wherein M is at least one cation having a valence n, Y is at least 5 andz is 0-40. M can be an alkali metal, e.g. sodium, and tetralkylammoniumcations, the alkyl group containing 2-5 carbon atoms.

Members of the family of zeolites designated herein as ZSM-5 have anexceptionally high degree of thermal stability thereby rendering themparticularly effective for use in processes involving elevatedtemperatures. In this connection, ZSM-5 zeolites appear to be one of themost stable families of zeolites known to date.

Members of the family of ZSM-5 zeolites possess a definitedistinguishing crystalline structure whose X-ray diffraction patternshows the following significant lines:

                  TABLE I                                                         ______________________________________                                        Interplanar Spacing d(A)                                                                           Relative Intensity                                       ______________________________________                                        11.1 ± 0.2        S                                                        10.0 ± 0.2        S                                                        7.4 ± 0.15        W                                                        7.1 ± 0.15        W                                                        6.3 ± 0.1         W                                                        6.04                                                                            ± 0.1           W                                                        5.97                                                                          5.56 ± 0.1        W                                                        5.01 ± 0.1        W                                                        4.60 ± 0.08       W                                                        4.25 ± 0.08       W                                                        3.85 ± 0.07       VS                                                       3.71 ± 0.05       S                                                        3.04 ± 0.03       W                                                        2.99 ± 0.02       W                                                        2.94 ± 0.02       W                                                        ______________________________________                                    

The unidentified crystalline material also produced crystallizes intolarge irregularly-shaped particles which are agglomerates of very smallplatelets. The crystalline product is relatively unstable and undergoesa loss in crystallinity and a large decrease in lattice parameter oncalcination. Crystallite size may have a bearing thereon.

The X-ray diffraction pattern of the unidentified crystalline materialof the present invention has the following values:

                  TABLE 2                                                         ______________________________________                                        Interplanar Spacing d(A)                                                                          Relative Intensity I/Io                                   ______________________________________                                        15.70               100                                                       8.01                2                                                         7.73                8                                                         7.25                5                                                         7.09                2                                                         5.64                2                                                         5.18                13                                                        5.01                8                                                         4.91                4                                                         4.59                3                                                         4.47                8                                                         4.36                3                                                         4.14                2                                                         4.00                4                                                         3.90                2                                                         3.63                17                                                        3.54                24                                                        3.44                70                                                        3.30                41                                                        3.21                14                                                        3.15                44                                                        2.99                2                                                         2.87                3                                                         2.82                3                                                         2.73                1                                                         2.64                3                                                         2.61                2                                                         2.59                3                                                         2.53                2                                                         2.42                1                                                         2.35                4                                                         2.31                2                                                         2.28                2                                                         2.06                1                                                         1.87                1                                                         1.84                3                                                         1.83                11                                                        ______________________________________                                    

These values for ZSM-5 and the unidentified material were determined bystandard techniques. The radiation was the K-alpha doublet of copper anda diffractometer equipped with a scintillation counter and a strip chartrecorder was used. The peak heights, I, and the positions as a functionof 2 theta, where theta is the Bragg angle, were read from thediffractometer chart. From these, the relative intensities, 100 I/I_(o),where I_(o) is the intensity of the strongest line or peak, and d(obs),the interplanar spacing in A, corresponding to the recorded lines, werecalculated. In the tables the relative intensities are given in terms ofthe symbols VS=Very Strong, S=Strong, M=Medium, W=Weak, and VW=VeryWeak, or numerically. It should be understood that each X-raydiffraction pattern is characteristic of all the species of each zeolitestructure, i.e. ZSM-5 and the unidentified product, respectively.

The sodium form of ZSM-5 as well as other cationic forms revealsubstantially the same pattern with some minor shifts in interplanarspacing and variation in relative intensity. Other minor variations canoccur depending on the silicon to aluminum ratio of the particularsample, as well as if it has been subjected to thermal treatment.

ZSM-5 can be used either in the alkali metal form, e.g. the sodium form,the ammonium form, the hydrogen form or another univalent or multivalentform. When used as a catalyst it will be subjected to thermal treatmentto remove part or all of any organic constitutent.

Zeolites ZSM-5, ZSM-11 and ZSM-12 have, for example, been originallycrystallized in the presence of quaternary ammonium compounds orprecursors thereof, e.g. ZSM-5, tetrapropylammonium ions, ZSM-11,tetrabutylammonium ions, and ZSM-12, tetraethylammonium (TEA) ions. Wehave found the methyl ANOxide cation to be effective in zeolitesynthesis. Depending upon the mixture composition, the product will beZSM-5 in low SiO₂ /Al₂ O₃ mixtures, the unidentified crystallinecomponent in very high SiO₂ /Al₂ O₃ mixtures, and a mixture of the twoat intermediate SiO₂ /Al₂ O₃.

By this invention it has been found that the crystalline materialscrystallize in the presence of the novel compounds 1-alkyl, 4-aza,1-azonia-bicyclo(2,2,2)octane, 4-oxide, halides.

The crystalline zeolites and the unidentified crystalline material canbe prepared from a reaction mixture containing a source of silica,optionally alumina, alkyl ANOxide cations (RNO), an alkali metal oxide,e.g. sodium, and water, and having a composition in terms of mole ratiosof oxides, falling within the following ratios:

    ______________________________________                                        For ZSM-5                                                                     REACTANTS     BROAD        PREFERRED                                          ______________________________________                                        SiO.sub.2 /Al.sub.2 O.sub.3                                                                 5 to 900     10 to 80                                           H.sub.2 O/SiO.sub.2                                                                         5 to 200     10 to 100                                          OH.sup.- /SiO.sub.2                                                                         0 to 1.0     0.1 to 0.5                                         M/SiO.sub.2   0.01 to 3.0  0.1 to 1.0                                         RNO/SiO.sub.2 0.01 to 2.0  0.05 to 1.0                                        For Unidentified Material                                                     REACTANTS     BROAD        PREFERRED                                          ______________________________________                                        SiO.sub.2 /Al.sub.2 O.sub.3                                                                 300 to 20,000                                                                              500 to 10,000                                      H.sub.2 O/SiO.sub.2                                                                         5 to 200     10 to 100                                          OH.sup.- /SiO.sub.2                                                                         0 to 1.0     0.1 to 0.5                                         M/SiO.sub.2   0.01 to 3.0  0.1 to 1.0                                         RNO/SiO.sub.2 0.01 to 2.0  0.1 to 1.0                                          For Mixtures of the Two                                                      REACTANTS     BROAD        PREFERRED                                          ______________________________________                                        SiO.sub.2 /Al.sub.2 O.sub.3                                                                 90 to 500    100 to 300                                         H.sub.2 O/SiO.sub.2                                                                         5 to 200     10 to 100                                          OH.sup.- /SiO.sub.2                                                                         0 to 1.0     0.1 to 0.5                                         M/SiO.sub.2   0.01 to 3.0  0.1 to 1.0                                         RNO/SiO.sub.2 0.01 to 2.0  0.1 to 1.0                                         ______________________________________                                    

the zeolites formed by the present invention form a class characterizedin their preparation by reaction mixtures of lower alkalinity and by azeolite product of SiO₂ /Al₂ O₃ >5. In addition they have a constraintindex of between 1 and 12.

The constraint index is calculated as follows: ##EQU1##

The constraint index approximates the ratio of the cracking rateconstants for the two hydrocarbons. Catalysts suitable for the presentinvention are those having a constraint index in the approximate rangeof 1 to 12. Constraint Index (CI) values for some typical catalysts are:

    ______________________________________                                               CAS             C.I.                                                   ______________________________________                                               ZSM-5           8.3                                                           ZSM-11          8.7                                                           ZSM-12          2                                                             ZSM-38          2                                                             ZSM-35          4.5                                                           TMA Offretite   3.7                                                    ______________________________________                                    

Crystallization can be carried out at either static or stirredcondition. In our examples static conditions were employed usingpolypropylene jars at 100° C. or stainless steel autoclaves at 160° C.The total useful range of temperatures is 80° C. to 180° C. for about 6hours to 150 days. Thereafter, the zeolite crystals are separated fromthe liquid and recovered. The composition can be prepared utilizingmaterials which supply the appropriate oxides. Reaction mixtures caninclude sodium silicate, silica hydrosol, silica gel, silicic acid, andsodium hydroxide, and of course, the alkyl ANOxide cations heretoforedescribed. The reaction mixture can be prepared either batch-wise orcontinuously. Crystal size and crystallization time of the zeolitecompositions will vary with the nature of the reaction mixture employedand the crystallization conditions.

As indicated above, the zeolite crystals prepared by the instantinvention are shaped in a wide variety of particle sizes. Generallyspeaking, the particles can be in the form of a powder, a granule, or amolded product, such as an extrudate having particle size sufficient topass through a 2 mesh (Tyler) screen and be retained on a 400 mesh(Tyler) screen. In cases where the catalyst is molded, such as byextrusion, the catalyst crystals can be extruded before drying or driedor partially dried and then extruded.

The zeolites prepared can also be used as a catalyst in intimatecombination with a hydrogenating component such as tungsten, vanadium,molybdenum, rhenium, nickel, cobalt, chromium, manganese, or a noblemetal such as platinum or palladium where ahydrogenation-dehydrogenation function is to be performed. Suchcomponent can be exchanged into the composition, impregnated therein orphysically intimately admixed therewith. Such component can beimpregnated in or on to it such as, for example, by, in the case ofplatinum, treating the zeolite with a solution containing a platinummetal-containing ion. Thus, suitable platinum compounds includechloroplatinic acid, platinous chloride and various compounds contianingthe tetrammineplatinum complex.

The above zeolite crystals especially in their metal, hydrogen, andammonium forms can be beneficially converted to a catalyticallyapplicable form by thermal treatment. This thermal treatment isgenerally performed by heating one of these forms in an atmosphere suchas air, nitrogen, steam etc., at a temperature of at lest 700° F. for atleast 1 minute and generally not more than 20 hours to remove part orall of the water and the organic constituent. While subatmosphericpressure can be employed for the thermal treatment, atmospheric pressureis desired for reasons of convenience. The thermal treatment can beperformed at a temperature up to about 1700° F. The thermally treatedproduct is particularly useful in the catalysis of certain hydrocarbonconversion reactions.

In the case of many catalysts it is desired to incorporate the zeolitewith another material resistant to the temperatures and other conditionsemployed in organic conversion processes. Such materials include activeand inactive materials and synthetic or naturally occurring zeolites aswell as inorganic materials such as clays, silica and/or metal oxides.The latter may be either naturally occurring or in the form ofgelatinous precipitates or gels including mixtures of silica and metaloxides. Use of a material in conjunction with the zeolite material,which is active, tends to improve the conversion and/or selectivity ofthe catalyst in certain organic conversion processes. Inactive materialssuitably serve as diluents to control the amount of conversion in agiven process so that products can be obtained economically and orderlywithout employing other means for controlling the rate of reaction.These materials may be incorporated into naturally-occurring clays, e.g.bentonite and kaolin, to improve the crush strength of the catalystunder commercial operating conditions. Said material, i.e. clays,oxides, etc., function as binders for the catalyst. It is required toprovide a catalyst having good crush strength because in commercial useit is desirable to prevent the catalyst from breaking down intopowder-like materials. These clay binders also improve the crushstrength of the catalyst.

Naturally-occurring clays which can be composited with the zeolitecrystals include the montmorillonite and kaolin family, which familiesinclude the subbentonites, and the kaolins commonly known as Dixie,McNamee, Georgia and Florida clays or others in which the main mineralconstituent is halloysite, kaolinite, dickite, nacrite, or anauxite.Such clays can be used in the raw state as originally mined or initiallysubjected to calcination, acid treatment or chemical modification.Binders useful for compositing with the catalyst also include inorganicoxides, notably alumina.

In addition to the foregoing materials, the zeolite catalysts can becomposited with a porous matrix material such as silica-alumina,silica-magnesia, silica-zirconia, silica-thoria, silica-beryllia,silica-titania as well as ternary compositions such assilica-alumina-thoria, silica-alumina-zirconia, silica-alumina-magnesiaand silica-magnesia-zirconia. The relative proportions of finely dividedcatalyst and inorganic oxide gel matrix vary widely with the zeolitecontent ranging from about 1 to about 90 percent by weight and moreusually, particularly when the composite is prepared in the form ofbeads, in the range of about 2 to about 50 percent by weight of thecomposite.

In order to more fully illustrate the nature of the invention and themanner of practicing same, the following examples are presented, whereinZSM-5, the unidentified crystalline material, and mixtures of both wereobtained.

In the examples which follow whenever adsorption data are set forth forcomparison of sorptive capacities for water, cyclohexane and n-hexane,they were determined as follows:

A weighed sample of the calcined adsorbent was contacted with thedesired pure adsorbate vapor in an adsorption chamber, evacuated to <1mm and contacted with 12 mm Hg water vapor or 20 mm Hg of cyclohexane orn-hexane vapor, pressures less than the vapor-liquid equilibriumpressure of the respective adsorbate at room temperature. The pressurewas kept constant (within about ±0.5 mm) by addition of adsorbate vaporcontrolled by a manostat during the adsorption period which did notexceed about eight hours. As adsorbate was adsorbed by thesilico-crystal, the decrease in pressure caused the manostat to open avalve which admitted more adsorbate vapor to the chamber to restore theabove control pressures. Sorption was complete when the pressure changewas not sufficient to activate the manostat. The increase in weight wascalculated as the adsorption capacity of the sample in g/100 g ofcalcined adsorbent.

EXAMPLES 1-3

The following examples, compiled as Table III, immediately hereinbelow,give details as to formulation, and reaction conditions, and theproducts obtained.

                  TABLE III                                                       ______________________________________                                        Crystallizations with Methyl ANOxide Cation                                   Q-brand; Al.sub.2 (SO.sub.4).sub.3 -16H.sub.2 O                                ##STR1##                                                                     H.sub.2 O/SiO.sub.2 = 40; Na.sup.+ /SiO.sub.2 = 0.6.sup.a                     Mixture Composition.sup.a                                                     Example                                                                              SiO.sub.2 /Al.sub.2 O.sub.3                                                              OH/SiO.sub.2                                                                           R/SiO.sub.2                                                                          Days Product                                ______________________________________                                        1       60        0.30     0.20   3    ZSM-5                                  2      120        0.30     0.20   3    ZSM-5 +                                                                       unidentified                                                                  crystalline                                                                   material                               3      ∞    0.30     0.20   3    unidentified                                                                  crystalline                                                                   material                               ______________________________________                                         .sup.a mole ratios                                                       

EXAMPLE 4

Hydrocarbon sorptions were conducted on the various products of Examples1-3 at different calcination temperatures. Results are compiled in TableIV.

                  TABLE IV                                                        ______________________________________                                        Product of               Weight Percent Sorbed                                Example Material   Treatment n-Hexane                                                                             cyclohexane                               ______________________________________                                        1       ZSM-5      600° C.                                                                          7.6    2.0                                       2       ZSM-5 +    300° C.                                                                          2.6    1.6                                               unidentified                                                                  crystalline                                                                   material                                                              2       ZSM-5      600° C.                                                                          5.9    1.0                                       3       unidentified                                                                             300° C.                                                                          0.4    --                                                crystalline                                                                   material                                                              ______________________________________                                    

Note that when the unidentified component of the product of Example 2 iscollapsed by calcination at 600° C., the n-hexane sorption more thandoubles (5.9 vs 2.6) suggesting higher catalytic activity.

What is claimed is:
 1. A method for preparing a synthetic crystallinezeolite material having a constraint index between 1 and 12 and and aSiO₂ /Al₂ O₃ ratio greater than 15 which comprises preparing a reactionmixture containing a source of an alkali metal oxide, an oxide ofsilicon, an oxide of aluminum, RNO, and water, and having a composition,in terms of mole ratios of oxides, falling within the followingranges:SiO₂ /Al₂ O₃ =5 to ∞ H₂ O/SiO₂ =5 to 200 OH⁻ /SiO₂ =0 to 1.0M/SiO₂ =0.01 to 3.0 RNO/SiO₂ =0.01 to 2.0wherein M is an alkali oralkaline earth metal and RNO 1-alkyl, 4-aza,1-azonia-bicyclo(2,2,2)octane, 4-oxide, halide and maintaining saidmixture under crystallization conditions until crystals of said zeoliteare formed.
 2. A method according to claim 1 wherein said mixture has acomposition, in terms of mole ratios of oxides, falling within thefollowing ranges:SiO₂ /Al₂ O₃ =10 to 10,000 H₂ O/SiO₂ =10 to 100 OH⁻/SiO₂ =0.1 to 0.5 M/SiO₂ =0.1 to 1.0 RNO/SiO₂ =0.1 to 1.0wherein M andRNO are as before.
 3. A method according to claim 1 wherein said SiO₂/Al₂ O₃ ratio is between about 5 and 90 and said zeolite materialfurther comprises ZSM-5.
 4. A method according to claim 1 wherein saidSiO₂ /Al₂ O₃ ratio is between 300 and 20,000.
 5. A method according toclaim 1 wherein said SiO₂ /Al₂ O₃ ratio is between about 90 and
 500. 6.A method according to claim 2 wherein said SiO₂ /Al₂ O₃ ratio is betweenabout 5 and 90 and said zeolite material further comprises ZSM-5.
 7. Amethod according to claim 2 wherein said SiO₂ /Al₂ O₃ ratio is between300 and 20,000.
 8. A method according to claim 2 wherein said SiO₂ /Al₂O₃ ratio is between about 90 and
 500. 9. A method according to claims 1,2, 3, 4, 5, 6, 7 or 8 wherein the 1-alkyl group is methyl or propyl. 10.A method according to claim 1 wherein substantially no alumina ispresent.